1. Field of the Invention
The present invention relates to a variable capacitance device whose capacitance value is changed by a control voltage value, and a communication apparatus including the same.
2. Description of the Related Art
Various variable capacitance devices whose capacitance values are changed according to a control voltage value have been proposed so far. For example, a variable capacitance device described in JP 11-260667 A has a stacked structure including capacitor electrodes disposed on both surfaces of a dielectric film for obtaining a large capacitance value, while being compact in size.
When a variable capacitance device is used, a control voltage application circuit is connected to a control terminal of the variable capacitance device for applying a control voltage to the variable capacitance device. However, when a high voltage is applied to the control voltage application circuit due to ESD (Electro-Static Discharge), a large surge current flows through the variable capacitance device, which might break the variable capacitance device.
In the case where a variable capacitance device is used for an electronic device for which a high voltage cannot be used, such as a cellular phone, a dielectric film used for the variable capacitance device has to be sufficiently thin in order to obtain a large amount of change in capacitance. In addition, an area of capacitor electrodes that sandwich the dielectric film has to be reduced for miniaturization. However, these restrictions deteriorate ESD resistance of the variable capacitance device.